1. Field of the Invention
The present invention generally relates to playback apparatuses and methods, programs, recording media, data structures, and manufacturing methods for recording media. More particularly, the invention relates to a playback apparatus and method, a program, a recording medium, a data structure, and a manufacturing method for the recording medium, which are suitably used when playing back streams.
2. Description of the Related Art
In digital versatile disc (DVD) video standards, interactive operations can be performed, that is, users can switch sound or subtitles when playing back AV content, such as a movie, recorded in an information recording medium (for example, see DVD Specifications for Read-Only Disc Part 3; Version 1.1). More specifically, in a display device 1 shown in FIG. 1, the user operates a sound switch button 11 or a subtitle switch button 12 of a remote controller 2 to switch sound or subtitles of AV content displayed on the display device 1. For example, if the user operates the sound switch button 11 when sound 1 is set in the initial state in the display device 1, sound 1 is switched to sound 2, as shown in FIG. 2.
AV content based on the DVD video standards is recorded in the form of a Moving Picture Experts Group (MPEG)2 program stream. In the MPEG2 program stream, as shown in FIG. 3, a video stream (indicated by “video” in FIG. 3), a plurality of audio streams (indicated by “audio 1”, “audio 2”, and “audio 3” in FIG. 3), and a plurality of sub-picture streams (indicated by “sub-picture 1, “sub-picture 2”, and “sub-picture 3”) are multiplexed such that the audio streams and the sub-picture streams are synchronized with the video stream. The sub-picture streams (sub-pictures 1, 2, and 3) are streams in which bitmap images are run-length coded, and are mainly used for subtitles.
Generally, a plurality of audio streams are used for recording sound of different languages, and a plurality of sub-picture streams are used for recording subtitles of different languages. The user can interactively select sound or subtitles of a desired language by using the remote controller 2 while video is being played back.
The DVD video standards define a table structure, provided to users, indicating the relationship between sound numbers and a plurality of audio streams (audio 1, 2, and 3) and the relationship between subtitle numbers and a plurality of sub-picture streams (sub-pictures 1, 2, and 3) in a program stream.
FIG. 4 illustrates an example of such a stream number table. In this table, the sound numbers are referred to as “A_SN (Audio Stream Numbers)”, and the subtitle numbers are referred to as “S_SN (Sub-picture Stream Numbers)”. In the stream number table shown in FIG. 4, each of the audio streams is provided with A_SN, and more specifically, A_SN=1: audio 2, A_SN=2: audio 1, and A_SN-3: audio 3. Also in FIG. 4, each of the sub-picture streams is provided with S_SN, and more specifically, S_SN=1: sub-picture 3, S_SN=2: sub-picture 1, and S_SN=3: sub-picture 2. In this case, a smaller number of A_SN or S_SN indicates an audio signal or a subtitle signal to be provided to users with higher priority. That is, A_SN=1 is an audio stream played back as a default, and S SN=1 is a sub-picture stream played back as a default.
More specifically, sound 1 played back in the initial state in FIG. 1 is audio 2, which is A_SN=1 (FIG. 4), and sound 2 played back after being switched from sound 1 in FIG. 2 is audio 1, which is A_SN=2.